Production of viscose rayon



dfidlfidii Patented Nov. 7, 1961 PRODUCTION F VISCOSE RAYON RichardElssner, Randerath, Germany, and Hugo Elling,

deceased, late of Oberbruch-Grebben, Germany, by

Gertrud Elling, sole heir, Oberbruch-Grebben, Germany, assignors toAmerican Enlra Corporation, Enka,

N.C., a corporation of Delaware No Drawing. Filed Dec. 19, 1953, Ser.No. 781,491

Claims priority, application Germany Jan. 4, 1958 3 Claims. (Cl. 18-64)This invention relates to the production of rayon threads and fibers andmore particularly to the production of such threads and fibers havinglow elongation values and high strength values.

The threads or fibers having such low elongation values and highstrength values find particular use in rubber products.

In order to define the relationship between the strength and elongation,the following formula has been developed: modulus M=1OO times breakstrength (grams/ den.):-elongation percent. Thus, if it is desired toobtain a thread or fiber of low elongation with a high break strength,it is necessary to obtain one with a high modulus.

In order to illustrate this comparison, the following Table I isprovided which compares the normal rayons (Nos. and 6) with cotton(No. 1) and certain special rayons (Nos. 2, 3 and 4).

It will be seen from an observation of this table that the moduli ofFortisan, a rayon produced by the saponification of acetate cellulose,and Lilienfeld rayon, are higher than that of cotton. However, both ofthese fibers are difficult to manufacture. Normal rayons show very lowmoduli which renders them undesirable, and it is only the special rayon(No. 4) which approaches the desirable modulus, but even this is lowerthan desired. This special rayon was prepared by viscose being spunafter addition of 1.5 grams per kilogram of viscose of an ethoxylatedcoconut oil amine in a spinning bath containing zinc sulfate andformaldehyde.

It is therefore an object of the present invention to provide a processfor manufacturing rayon threads and fibers of improved physicalproperties.

An additional object of the present invention is to provide a simple andeconomical process for manufacturing rayon blends and fibers of lowelongation values and high strength values.

it is a further object of this invention to provide a rayon fiber orthread having low elongation value and high strength value.

It has been found by the present invention that rayon threads and fibersof low elongation values and high breaking strength and therefore highmoduli can be obtained by adding to the viscose rayon solution awatersoluble alkali metal salt of a strong acid. Up to 50 grams/ kg. ofsuch a salt may be added. This will be in addition to the use ofalso-called modifier in the viscose, such as an ethoxylated amine orsimilar agent such as ethoxylated fatty acids or alcohols, polyethyleneglycols, amines, polyamines, quaternary ammonium compounds,

or their ethoxylated derivatives. The modifier may be present to theextent of 0.3 to 3.0 grams/kg. of viscose.

The preferred method of accomplishing this invention is to add thealkali metal salt to the caustic soda dissolving solution for thecellulose Xanthate.

The thus obtained viscose, after it has been filtered, deaerated, andfinally ripened in the known manner, is spun into a spin bath containingsulfuric acid, zinc sulfate and sodium sulfate. The thread or fiber isthen passed into an intermediate bath containing sulfuric acid, Zincsulfate, sodium sulfate and preferably formaldehyde, and finally into asecond acid bath containing sulfuric acid, zinc sulfate, sodium sulfateand preferably formaldehyde in different concentrations than used ineither the first acid bath or the intermediate bath. Thereafter thethread or fiber thus obtained is simultaneously stretched and dried.

The alkali metal salt of the strong acid may be any one of the followingwhich have been found to accomplish the objects of this invention:sodium sulfate, sodium chloride, potassium sulfate, potassium chloride,sodium nitrate or potassium nitrate. The alkali metal salts ofphosphoric acid have been found to give a lower moduli than the abovelisted salts. The salts of weak acids are ineffective and will notaccomplish the objects of this invention.

The following Tables II and III illustrate the effect of using variousquantities of sodium sulfate and sodium chloride, respectively, in theprocess of this invention. These salts were added, together with 1.5grams of an ethoxylated coconut oil amine of a molecular weight of about1100 per kilogram of viscose.

Table II Amount of Strength, Elongation, Modulus Na SOi g./den. percentNo. added to the viscose,

gjkg. dry wet dry wot dry wet Table III Strength, Elongation, ModulusAmount of N aOl added to the gJden. percent viscose, gjkg. dry wet drywot dry wet l 5.1 4.1 14 j 28 3e 15 5.0 3.8 11 1 23 46 17 5.2 4.0 9 2157 19 5.4 4.0 8 20 67 20 Thus the alkali metal salt may be added inproportions of 350 grams/kg. of viscose.

In addition, cords manufactured from the thus treated viscose and havingthe construction 1650 den. 1 x 2 ZXS 12 x 12 revealed thecharacteristics as shown in Table IV.

Table IV Cord 00nd. Cord ovendried Strength, Elonga Strength,Elongag./den. tion, Modulus g./den. tion, Modulus Percent Percent It hasbeen shown that in the preferred operation of this invention the alkalimetal salt is added to the viscose followed by addition of anethoxylated coconut oil amine. This amine has the general formula:

in which n is between 8 and 14, x plus y=about 20 and and the molecularweight is about 1100.

In addition to this amine, other compounds such as ethoxylated fattyacids, ethoxylated fatty alcohols, polyethylene glycols, amines,polyamines, quaternary ammonium compounds, or their exthoxylatedderivatives may also be used. These addition agents may be added inproportion of 0.3 to 3.0 grams/ kg. of viscose with the preferredproportion being 1.5 grams/ kg.

It is known that the breaking strength and therefore the moduli ofthreads and fibers may be increased further by stretching the thread orfiber during their drying which follows the second acid bath. Inaddition, further improvement may be obtained by adding to theintermediate bath 0.5 to 5% of formaldehyde.

The following Tabe V illustrates the effect of these two aids. Theorganic additive used in the examples below was used in theseexperiments.

Table V Strength, ElongagJden. tion, Modulus HCOH Drypercent iug dry wetdry Wet dry Wet Without NazSO4.---- 3. 8 3.1 29 32 13 With NazSOt.-. 3.4 2. 4 14 19 24 13 with Na2SO4 3. 8 2. 7 8 8 48 33 with NiqSO4--- 4. 63. 3 9 10 51 32 in which n is between 8 and 14, x plus y=about and themolecular weight is about 1100, is added to the viscose in theproportion of 1.5 grams/ kg. of viscose.

This viscose, following filtering, deaeration, and ripening in the knownmanner, is spun with a gamma number of about 48 and a viscosity by theball-falling test of 93 seconds. A spinning nozzle having 1000 orificesof a diameter of 60 microns each is used to obtain a titre of 1650denier.

The spun thread runs from the spinning nozzle through a horizontallydisposed tube of a length of 50 cm. and an internal diameter of 20 mm,which tube is submerged in an acid spinning bath. This bath ismaintained at 48 C. and contains 4.3% sulfuric acid, 13.0% sodiumsulfate, and 6.0% zinc sulfate. The spun thread leaves the tube andpasses over a guide roller to a godet rotating at 19 m./ min.

The thread is caused to travel four times around this godet by a groovedroller arranged below it. This grooved roller is submerged in aso-called intermediate bath containing 22 grams/kg. sulfuric acid,grams/kg. sodium sulfate, 38 grams/ kg. zinc sulfate, and 18 grams/kg.formaldehyde and maintained at 30 C. The above proportions are expressedin grams per kilogram of bath solution.

From this intermediate bath, the thread passes around a second godet,rotating at a speed of 40 m./min., and through a second acid bath. Thissecond acid bath contains 15 grams/kg. sulfuric acid and small amountsof sodium sulfate, zinc sulfate and formaldehyde. The proportion of thesulfuric acid is based on the total bath composition. The trajectorylength of this second acid bath is 140 cm.

The thread passes from this second acid bath around a third godetrotating at 35.8 rn./min., into a slowly rotating bucket. The mass ofthreads While remaining in this bucket is deacidified, desulfurized andsized by any methods known in the art. Thereafter, the thread is removedfrom the bucket and stretched 11% in a final stretching assembly Whilebeing simultaneously dried.

The thread produced by this method is indicated in Table II as No. 6.The thread has a very desirable high breaking strength, low elongationvalue and therefore a high modulus.

In the operation of this invention, cellulose of any origin may be used,such as linters, high-grade celluloses, and standard rayon celluloses.It is possible to vary the cellulose content or the cellulose/causticratio without departing from the scope of this invention.

The viscose solutions obtained by the process of this invention are spunwith a gamma number between 56 and 35 into acid baths which containpreferably more than 20 grams/ kg. of zinc sulfate. In addition, thespinning baths may contain viscose and/or spinning auxiliaries such alauryl pyridinium chloride, or other surface-active agents.

While the present invention has been described in a preferred manner, itwill be understood that many changes and modifications may be made inthe methods of procedure without departing from the scope of thisinvention.

What is claimed is:

1. A process for the production of high strength viscose rayon threadsand fibers having a high modulus determined by the following formula: MS divided by E, wherein M is the modulus, S is the dry strength in gramsper denier, and E is the dry elongation, which comprises extrudingviscose containing about 3.0 to 50 grams per kilogram of viscose, of analkali metal salt of the class consisting of sodium sulfate andpotassium sulfate, about 0.3 to 3.0 grams per kilogram of viscose, of amodifier of the class consisting of polyethylene glycols, ethoxylatedamines and their quaternizedderivatives, into an aqueous acidzinc-containing spin bath, passing the thus produced threads to anintermediate bath containing formaldehyde, and finally collecting thethreads.

2. A process according to claim 1 in which the alkali metal salt issodium sulfate.

3. A process according to claim 1 in which the modifier is ethoxylatedcoconut oil amine of the general formula:

(CH2. SE20) XH Cn 2n+l N (enacmonn in which n is between 8 and 14 and xplus y equals about 20.

4. A process according to claim 1 in which about 0.5% to 5.0% by weightof formaldehyde is used in the intermediate bath.

5. A process according to claim 4 in which the intermediate bath ismaintained at about room temperature.

6. A process according to claim 5 in which the threads after having beencollected and purified are dried under tension.

7. A process for the production of high strength vis- M=100 S divided byE wherein M is the modulus, S is the dry strength in grams per denier,and E is the dry elongation, which comprises extruding viscosecontaining about 3.0 to 50 grams per kilogram of viscose, of an alkalimetal salt of the class consisting of sodium sulfate and potassiumsulfate, about 0.3 to 3.0 grams per kilogram of viscose, of a modifierof the class consisting of polyethylene glycols, ethoxylated amines andtheir quaternized derivatives, into an aqueous acid zinc-containing spinbath, passing the thus produced threads to an intermediate bathcontaining taining formaldehyde, and finally collecting the same. 8. Aprocess according to claim 7 in which the threads after having beencollected and purified are dried under tension.

References Cited in the file of this patent formaldehyde, passing thethreads to a third bath con- 15 2,937,070

UNITED STATES PATENTS Coe Apr. 6, 1948 Kayser Oct. 26, 1948 ThurmondOct. 23, 1951 Lekkerkerker Apr. 2, 1957 Cox et a1. Sept. 16, 1958Hollihan et a1. Sept. 16, 1958 Cox May 17, 1960

1. A PROCESS FOR THE PRODUCTION OF HIGH STRENGTH VISCOSE RAYON THREADSAND FIBERS HAVING A HIGH MODULES DETERMINED BY THE FOLLOWING FORMULA:M=100XS DIVIDED BY E, WHEREIN M IS THE MODULUS, S IS THE DRY STRENGTH INGRAMS PER DENIER, AND E IS THE DRY ELONGATION, WHICH COMPRISES EXTRUDINGVISCOSE CONTAINING ABOUT 3.0 TO 50 GRAMS PER KILOGRAM OF VISCOSE, OF ANALKALI METAL SALT OF THE CLASS CONSISTING OF SODIUM SULFATE ANDPOTASSIUM SULFATE, ABOUT 0.3 TO 3.0 GRAMS PER KILOGRAM OF VISCOSE, OF AMODIFIER OF THE CLASS CONSISTING OF POLYETHYLENE GLYCOLS, ETHOXYLATEDAMINES AND THEIR QUATERNIZED DERIVATIVES, INTO AN AQUEOUS ACIDZINC-CONTAINING SPIN BATH, PASSING THE THUS PRODUCED THREADS TO ANINTERMEDIATE BATH CONTAINING FORMALDEHYDE, AND FINALLY COLLECTING THETHREADS.